Host sex and life stage modulate the effect of diet on gut microbial communities. crayfish microbiome

Individual hosts can be viewed as patches of habitat that are colonized by microbes compatible with the host environment. The host environment is dynamic, and it is unclear how variation of the host traits alters microbial communities. We conducted a manipulative experiment in the laboratory to understand how host diet, ontogenetic stage, and sex alter gut microbial communities in signal crayfish (Pacifastacus leniusculus). We found one core taxa among all crayfish and gut microbial composition similar to their food items, suggesting that gut microbes are transient and largely related to diet. In turn, microbial functional potential is also closely related to diet. We also found interactions between life stage (juvenile and adult) and sex, as well as between sex and diet in shaping the gut microbiota of crayfish. Differences between juveniles and adults are likely due to physiological changes that accompany reproductive organ growth and hormonal changes. Behavioral differences between male and female crayfish as well as hormonal differences between the sexes may be responsible for sex-dependent differences in gut microbial communities for crayfish in the wild. Though diet, ontogenetic stage, and sex were important factors for crayfish gut microbial communities, their low explanatory power suggests that other factors, such as dynamics occurring at different scales or feedbacks between host and microbes, are driving variation in gut microbial communitites.